Joined: Jun 2021 Posts: 61 Threads: 22
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Location: Nottingham England
Car type: Austin seven Box saloon 1935
I have replaced the head gasket on my seven and removed the manifold also, before setting the tappet clearance, I looked at the manifold and it appears there are only two inlet branches off the manifold on a four cylinder car, how does this work as I can't set the tappets without identifying the inlet and exhaust valves ?
I must be missing something here
Explanations gratefully received
Cheers
Mike
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14-07-2021, 03:48 PM
(This post was last modified: 14-07-2021, 03:58 PM by JonE.)
if you put your finger in all 6 of the holes, you will see the "pairing" of the inlets by which ones aren't sooty.
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No such thing as a silly question Mike.
The inlet ports are 'siamesed' i.e. they blend into one, so counting the valves from the front 1st is #1 exhaust, 2nd is #1 inlet; 3rd is #2 inlet, which shares the same port as #1, followed by #2 exhaust; then the pattern is repeated.
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14-07-2021, 03:51 PM
(This post was last modified: 14-07-2021, 03:52 PM by Stuart Giles.)
The inlet ports are 'siamesed' meaning that each port serves two valves. So, starting from the front of the motor you have: exhaust valve, inlet valve, inlet valve, exhaust valve, exhaust valve, inlet valve, inlet valve exhaust valve.
Edit, need to type faster!
Joined: Aug 2017 Posts: 926 Threads: 22
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Location: Near Cambridge, UK
Car type: 1928 tourer (mag type), short chassis Gould Ulster
As you go aong the block, you get exhaust, inlet branching inside the block, exhaust, exhaust, inlet branching again, and exhaust. To make sure each vave is fully closed for setting clearance make sure that a corresponding valve is fully open, ie set no 1 when 8 is fully open, 2 when 7 is fully open, 3 when 6 is fully open, and so on along the length of the block.
Joined: Jun 2021 Posts: 61 Threads: 22
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Location: Nottingham England
Car type: Austin seven Box saloon 1935
Thanks all I have worked on all sorts but this threw me you live and learn
What a great forum group had an answer in 15 minutes!
Invaluable
Good luck to all seveners hoping to be on the road for the weekend
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Location: Auckland, NZ
Siamesed ports were common on most side valve engines and many overhead. More power can be extracted with separate ports. BMC retained late with little penalty cf contemporaries. Hot Minis develop staggering bhp
